The supply of fossil fuels is slowly being exhausted, and burning gasoline is causing much environmental pollution. Electric vehicles (EVs) are the future of transportation, but their batteries have some critical shortcomings: short range of vehicles, short service life, and high costs, preventing widespread consumer adoption. Regulating the battery temperature during continuous charge and discharge is a major challenge.
For most Li-ion batteries used in EVs, their temperature specification is normally as follows:
Operating temperature: −20° C. to 60° C.
Charging temperature: 0° C. to 45° C.
Storage temperature: −10° C. to 45° C.
They can achieve their rated capacity at 20˜25° C. and their capacity will drop ˜10% for every increase of 10° C.
During winter, when temperatures can easily fall below 0° C., it will be difficult or totally impossible for charging.
During other seasons, under continuous high current charge/discharge, the battery working temperature can easily reach 60° C., making it difficult for discharging. Higher temperatures can also cause battery degradation, shortened service life, or present safety hazards.
The specific characteristics of Li-ion cells require well-adapted and well-designed battery temperature management and control systems.
In the subsequent paragraphs, for simplification, the word ‘cooling’ will represent heat exchange, be it cooling or heating, and the word ‘coolant’ will represent a liquid that has anti-freeze, non-flammable, non-corrosive and anti-fungal properties for heat exchange of the battery cells, be it for cooling or heating.